Today I watched an archaeology class learn how to use a total station. It was painful to watch.
Some quotes: "I can't see any white triangle." "What do you mean, crosshairs?" "Uh, maybe you should lock the motions before using the fine adjust knobs." I was also a little nervous that they let it get set up with about 18 inches between tripod legs. It looked like a stiff wind could blow it over, but the assistant in charge didn't comment.
What really got me was that I think it took 10 minutes to set up over a point. The procedure was to put a cap on the tripod, that centered the 5/8" screw, hang a plumb bob, readjust the length of its string, fiddle with the legs until it was close, check the level of the tripod head, repeat for a while, put the TS on and find that it wasn't close enough, and start over.
The professor won't let them change the length of a tripod leg after mounting the total station. Since the optical plummet is in their total station and not the tribrach, that prevents the procedure I always use (Wolf & Ghilani 8.5).
Using that, you get in the ballpark, use the tribrach screws to point at the ground mark, adjust the tripod legs to nearly level the tribrach, and you are probably close enough to slide the tribrach into position. I do cheat and leave the instrument on the tribrach while making small adjustments to one leg at a time, and W&G say you shouldn't.
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So the question is: Do you or do you let your crews adjust the length of one tripod leg at a time with the instrument in place?
I'm not nearly talented enough to set up quickly otherwise.
Why yes! Expressly with a laser plummet.
Absolutely! And I have it set up faster than anyone else I have observed.
It all began with first order deformation monitoring surveying in northern Canada, where we would set up a handful of targets and then observe them numerous times from two setups on the bottom and two setups on the top.
As this involved setting up a set of legs as low as possible, and then setting a tall set of legs overtop the short set, (each pointed at the respective observation point), I was really struggling centering over such a high point. The kind party chief, saw this, and told me he was going to show me a trick to drastically improve things. And that was it.
The best part was repeatedly stumping my instructors as to how I was setting up so fast once I was in school.
> So the question is: Do you adjust the length of one tripod leg at a time with the instrument in place?
Obviously. You
1) rough center the tripod over the ground mark by whatever effective means come to mind,
2) attach the instrument to the tripod, and
3) point the optical plummet at the ground mark by adjusting the tribrach screws.
Then you
4) adust the tripod legs to center the circular plate vial on the instrument,
5) level with the tubular vial and
6) shift the instrument to bring the plummet crosshairs onto the ground mark.
7) refine levelment using compensator in instrument
8) shift the instrument to center on ground mark if needed.
Repeat steps 7 and 8 as needed.
4 of 4 so far. I'm relieved that you wouldn't yell at me for doing it.
That professor would yell. Maybe he's justified considering how raw the students are?
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Another thing bothered me. This is in a Corps of Engineers park with an archaeological site the classes come back to year after year. Several reference points (I saw at least 6) for topo of the area, which I understand are left in place from year to year, are uncapped 3/8" rods (rebar?) with 1/2" to 3/4" left sticking up above ground. I suppose he doesn't pound them below grade because he doesn't have a magnetic locator.
This looks like a hazard in that a hiker in some other season could stomp down on one and run it through the sole of their tennies into their foot. Or at least someone could trip on it and disturb its horizontal location. Or maybe pull it if they had a leatherman tool. Or find a rock and pound it further into the ground so the vertical datum is wrong next year.
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I guess I'm getting opinionated in my old age, but it's hard to keep my mouth shut while watching.
> I guess I'm getting opinionated in my old age, but it's hard to keep my mouth shut while watching.
Well, they ARE archaeologists. Why would one expect any sophistication at all from them in matters of surveying? That isn't how reputations are made.
Yes!
Exactly the method the Wild salesman demonstrated when I bought a Wild T2/Di10 Distomat, along with its 9 prism configuration, June 1972. And, I have been using the same method ever since.
Most people I observe setting up, have their eyeball glued to the optical plummet while they walk around carrying the instrument looking to find the point. Those using a laser dot typically carry the instrument around also.
(ubenhavin?)
Make that 5 of 5.
> ...So the question is: Do you or do you let your crews adjust the length of one tripod leg at a time with the instrument in place?
Of course.
Being schooled early in my career with "stiff-legged" K&E tripods, I found adjustable legs to be just as innovative as sliced bread; a veritable "breath of fresh air" to any instrument man.
If you want to have a good laugh, extend the tripod legs out all the way and ask a younger member of the profession to then set up an instrument without adjusting the legs. 😉
> So the question is: Do you or do you let your crews adjust the length of one tripod leg at a time with the instrument in place?
Yes, with a firm grip.
I was recently on vacation in Ephesus Turkey looking at the ancient ruins. I saw archaeological control points around the ancient city. Some of the placements of those control points were a little irregular. They were on loose stones along tourist footpaths. It seemed like they were pretty easy to disturb by tourists. I was thinking there's no way I'd be caught putting a control point in such a shoddy spot.
Yes, and the firm grip is important.
I always taught people to grip the leg with their thumb on top of the lower leg section and wrapped around one of the rods of the upper section. You loosen the adjusting knob or lever only after you have a good grip on the leg. The TS isn't going to receive any major jolt or shock if you control the leg in that way.
I learned this setup method with T-1s and T-16s about 1975. It was in a MnDOT manual at the time.
There was one crusty old-timer I worked for who didn't believe in sliding-leg tripods. His crews carried nothing but stiff-legs. Lots of fun with those when setting up on a steep bank about a foot from a chain link fence.
> > So the question is: Do you adjust the length of one tripod leg at a time with the instrument in place?
>
> Obviously. You
>
> 1) rough center the tripod over the ground mark by whatever effective means come to mind,
> 2) attach the instrument to the tripod, and
> 3) point the optical plummet at the ground mark by adjusting the tribrach screws.
>
> Then you
>
> 4) adust the tripod legs to center the circular plate vial on the instrument,
> 5) level with the tubular vial and
> 6) shift the instrument to bring the plummet crosshairs onto the ground mark.
>
> 7) refine levelment using compensator in instrument
> 8) shift the instrument to center on ground mark if needed.
>
> Repeat steps 7 and 8 as needed.
This, but step 9 being turn the instrument 90 and half the bubble error to plumb.
Yes, even with my S8 o.O
No! Tripod/Total Station setup procedures
> So the question is: Do you or do you let your crews adjust the length of one tripod leg at a time with the instrument in place?
Well, um, No, actually. I don't. That is, I don't forbid it, but it shouldn't be happening.
Because I prefer that they set up the legs with the TRIBRACH ONLY on the legs. Once the legs are levelled up and centered with the tribrach, then and only then the instrument comes out of the box and is placed on the tribrach, and locked in place. Proceed with fine tuning, which should not involve messing with the length of the legs at that point.
> > Then you
> >
> > 4) adust the tripod legs to center the circular plate vial on the instrument,
> > 5) level with the tubular vial and
> > 6) shift the instrument to bring the plummet crosshairs onto the ground mark.
> >
> > 7) refine levelment using compensator in instrument
> > 8) shift the instrument to center on ground mark if needed.
> >
> > Repeat steps 7 and 8 as needed.
>
>
> This, but step 9 being turn the instrument 90 and half the bubble error to plumb.
Yes, if anyone is taking this checklist into the field, note that leveling the instrument with the tubular vial requires checking the vial in two perpendicular positions. If the vial is in good adjustment, the bubble should be centered in the vial when the vial is level, so keep that in mind when checking the vial.
No! Tripod/Total Station setup procedures
Agreed, that is better if you have the option. Some instruments (like the ones I saw in use) have the plummet in the instrument and not in the tribrach.
No! Tripod/Total Station setup procedures
> ... Some instruments have the plummet in the instrument and not in the tribrach.
IMO, that would be a deal killer for me. I would not purchase such an instrument. But I have seen them, I know that they exist.
No! Tripod/Total Station setup procedures
Having the optical plummet in the instrument actually has its advantages, mainly that you can check the plummet after the setup by rotating the instrument after being centered and leveled by making sure the crosshairs (or laser) do not move around the point you are setup on!
Taught this method in basic surveying classes for many (more than I want to admit) years. However, once the tripod was roughly over the point and legs evenly spaced step the legs firmly into the ground!!! Don' know how many times I had to yell at students "ONE PERSON ADJUSTING ONE LEG AT A TIME!!!" Strange how they wanted to get three people, one on each leg, and adjust everything at the same time. Totally defeats the adjustment procedure.
